ssh/sftp: realign struct for better size allocation

The realignment reduce the cost of the following struct,

* Client: from 88 to 80 bytes (-8)
* dirEntry: from 40 to 32 bytes (-8)
* FileAttrs: from 72 to 64 bytes (-8)
* packet: from 128 to 88 bytes (-40)

While at it, add missing comment to FileHandle type.

5 files changed, 36 insertions, 27 deletions

diff --git a/lib/ssh/sftp/client.go b/lib/ssh/sftp/client.go
index 6d5da1ab..dbad2f0b 100644
--- a/lib/ssh/sftp/client.go
+++ b/lib/ssh/sftp/client.go
@@ -18,8 +18,8 @@ import (
 
 // Client for SFTP.
 type Client struct {
-	sess    *ssh.Session
-	version uint32
+	sess *ssh.Session
+
 	exts    extensions
 	pipeIn  io.WriteCloser
 	pipeOut io.Reader
@@ -27,8 +27,11 @@ type Client struct {
 
 	// The requestId is unique number that will be incremented by client,
 	// to prevent the same ID generated on concurrent operations.
-	mtxId     sync.Mutex
 	requestId uint32
+
+	version uint32
+
+	mtxId sync.Mutex
 }
 
 // NewClient create and initialize new client for SSH file transfer protocol.
diff --git a/lib/ssh/sftp/dir_entry.go b/lib/ssh/sftp/dir_entry.go
index dae071c0..dd3ef4e3 100644
--- a/lib/ssh/sftp/dir_entry.go
+++ b/lib/ssh/sftp/dir_entry.go
@@ -9,9 +9,10 @@ import "os"
 // dirEntry represent the internal data returned from Readdir, Readlink, or
 // Realpath.
 type dirEntry struct {
+	attrs *FileAttrs
+
 	fileName string
 	longName string
-	attrs    *FileAttrs
 }
 
 func (de *dirEntry) Name() string {
diff --git a/lib/ssh/sftp/file_attrs.go b/lib/ssh/sftp/file_attrs.go
index ab93c114..a5e8c870 100644
--- a/lib/ssh/sftp/file_attrs.go
+++ b/lib/ssh/sftp/file_attrs.go
@@ -36,16 +36,20 @@ const (
 
 // FileAttrs define the attributes for opening or creating file on the remote.
 type FileAttrs struct {
-	name        string
+	exts extensions // attr_EXTENDED
+
+	name string
+
+	fsMode fs.FileMode
+
+	size uint64 // attr_SIZE
+
 	flags       uint32
-	size        uint64     // attr_SIZE
-	uid         uint32     // attr_UIDGID
-	gid         uint32     // attr_UIDGID
-	permissions uint32     // attr_PERMISSIONS
-	atime       uint32     // attr_ACMODTIME
-	mtime       uint32     // attr_ACMODTIME
-	exts        extensions // attr_EXTENDED
-	fsMode      fs.FileMode
+	uid         uint32 // attr_UIDGID
+	gid         uint32 // attr_UIDGID
+	permissions uint32 // attr_PERMISSIONS
+	atime       uint32 // attr_ACMODTIME
+	mtime       uint32 // attr_ACMODTIME
 }
 
 // NewFileAttrs create and initialize FileAttrs from FileInfo.
@@ -191,6 +195,7 @@ func (fa *FileAttrs) Mode() fs.FileMode {
 	return fa.fsMode
 }
 
+// Name return the name of file.
 func (fa *FileAttrs) Name() string {
 	return fa.name
 }
diff --git a/lib/ssh/sftp/file_handle.go b/lib/ssh/sftp/file_handle.go
index 71c4ed81..d20b01b9 100644
--- a/lib/ssh/sftp/file_handle.go
+++ b/lib/ssh/sftp/file_handle.go
@@ -4,6 +4,7 @@
 
 package sftp
 
+// FileHandle define the container to store remote file.
 type FileHandle struct {
 	remotePath string // The remote path.
 	v          []byte // The handle value returned from open().
diff --git a/lib/ssh/sftp/packet.go b/lib/ssh/sftp/packet.go
index 373281e2..4f7b24f3 100644
--- a/lib/ssh/sftp/packet.go
+++ b/lib/ssh/sftp/packet.go
@@ -47,21 +47,16 @@ const (
 // )
 
 type packet struct {
-	length    uint32
-	kind      byte
-	requestId uint32
+	// FxpHandle
+	fh *FileHandle
 
-	// FxpVersion.
-	version uint32
-	exts    extensions
+	// FxpAttrs
+	fa *FileAttrs
 
-	// FxpStatus
-	code        uint32
-	message     string
-	languageTag string
+	exts extensions // from FxpVersion.
 
-	// FxpHandle
-	fh *FileHandle
+	message     string // from FxpStatus
+	languageTag string // from FxpStatus
 
 	// FxpData
 	data []byte
@@ -69,8 +64,12 @@ type packet struct {
 	// FxpName
 	nodes []*dirEntry
 
-	// FxpAttrs
-	fa *FileAttrs
+	version   uint32 // from FxpVersion.
+	code      uint32 // from FxpStatus
+	length    uint32
+	requestId uint32
+
+	kind byte
 }
 
 func unpackPacket(payload []byte) (pac *packet, err error) {